Snakes in the Attic?

A few days ago, the Orkin termite inspector did an inspection of our house.  While he didn't find any termites, he did note that the screen covering a vent on the west gable end of our attic was pulled open, and that there was a huge squirrel's nest below it.

He stated that squirrels pulled the screen down and built the nest.  He said that Orkin could staple the screen back up, clear out the nest, and put down a few inches of TAP (Thermal Acoustical Pest Control), a blown-in cellulose type of insulation laced with boric acid.  He said that the boric acid would kill any insect infestation, and would repel the squirrels.  Cost would be about $1000-$2,200, depending on the thickness of the TAP.

I was extremely surprised that the screen was pulled down.  A couple of years ago, I had gone up there and found the screen for that vent totally torn-up, and that huge nest below the vent.  I thought it was a bird's nest because I found about 15 dead birds up in the attic.  So I replaced the torn screen with an aluminum fine-meshed screen (the kind for windows), and a 1/4" "hardware cloth" (a mesh made of galvanized steel, I think). I left the nest because...well...it was huge and I was lazy.  Anyway, I stapled the screen and hardware cloth up with probably 50+ staples, so I was quite shocked that the screen was partly pulled off.

Well, I went up there today and found that although the hardware cloth was partly pulled down, the fine-meshed screen was still intact.  Basically, nothing could get through it.  So, it occurred to me that either the hardware cloth came off by itself (unlikely), or someone pulled it off.  Now, I am the only one in my family that goes up there.  I was up there last December or January, and everything was intact.  So I suspect that the Orkin guy pulled the hardware cloth, leaving the fine-meshed screen.  I decided to repair this thing so nothing, not even an Orkin guy could pull it off.  I used some 1" #10 stainless steel screws, with 1 1/4" washers:

After screwing down the hardware cloth with some of these and adding about 50 more staples, it was fixed:

I then decided to check the east gable vent.  To my surprise, there some rather large wasp nests on the it inside the attic:

Close inspection revealed holes in its metal screen, probably pecked out by birds or a squirrel.  So I put a new screen on to cover the entire vent.

I also found something while up there that totally shocked me.  Check it out:

A shedded (molted?) snake skin!!  What would a snake be doing up there?  How would it get up there?  Maybe somebody put it up there?  The Orkin guy?  Anyway, weird.  I don't think there are any snakes up there now.  I had spend a lot of time up there in the past couple of years, and had never seen any snakes or signs of snakes.